GN have devoted to oil sludge treatment system for a long time, and have succeed in many sites, also with different equipment combination, now the system has been optimized. Below link shows one demo test in a China site:

It differs from different sources also, oily sludge from oil refinery, and Oil&gas Drilling Mud/Waste Oil Pit Mud.The
current treatment of oily sludge and sewage sludge from oil refinery
includes incineration and landfill. The former requires high cost while
the latter cannot achieve pollution abatement radically. But by using a
dehydration-drying-carbonization process to treat the toxic wastes,
recycle oil and energy, and produce useful final products. This is a
significant breakthrough in oily sludge treatment field.The random
disposal of oily mud and waste from drilling and transportation on site
without treatment cause permanent pollution to the soil and underground
water. It’s extremely difficult to effectively treat this oily mud and
waste because it is scattered around the vast oil field and its
composition is very complex. Under the stricter and stricter
environmental regulations in these years, oil producers are facing the
urgency of permanently treat this notorious industrial “junk”. The
reasons why some Chinese oil producers failed to solve the problems by
applying imported technologies and equipment from abroad are the special
domestic conditions and high cost.

GN is nowadays also on progress of developing our own TDU, thermal desorption unit, contact GN for more if you want.